Team size matters: Collaboration and scientific impact since 1900

Team size matters: Collaboration and scientific impact
since 1900
Vincent Larivière 1,2, Cassidy R. Sugimoto 3, Andrew Tsou 3, and Yves Gingras 2
1. École de bibliothéconomie et des sciences de l'information, Université de Montréal, C.P. 6128,
Succ. Centre-Ville, Montréal, QC. H3C 3J7, Canada
2. Observatoire des Sciences et des Technologies (OST), Centre Interuniversitaire de Recherche
sur la Science et la Technologie (CIRST), Université du Québec à Montréal, CP 8888, Succ.
Centre-Ville, Montréal, QC. H3C 3P8, Canada
3. School of Informatics and Computing, Indiana University, 1320 E. 10thSt, Bloomington, IN.
47405, USA
[[email protected]; [email protected]; [email protected];
[email protected]]
This paper provides the first historical analysis of the relationship between collaboration and
scientific impact, using three indicators of collaboration (number of authors, number of addresses,
and number of countries) and including articles published between 1900 and 2011. The results
demonstrate that an increase in the number of authors leads to an increase in impact–-from the
beginning of the last century onwards—and that this is not simply due to self-citations. A similar
trend is also observed for the number of addresses and number of countries represented in the
byline of an article. However, the constant inflation of collaboration since 1900 has resulted in
diminishing citation returns: larger and more diverse (in terms of institutional and country
affiliation) teams are necessary to realize higher impact. The paper concludes with a discussion of
the potential causes of the impact gain in citations of collaborative papers.
The notion of the lone genius is one of science’s keystone myths, simultaneously romantic and
tidy. The quintessential example is that of Einstein conducting cutting-edge research while
working as an examiner at the Bern patent office (Pyenson, 1985; Simonton, 2013). However, as
with many myths, the “lone genius” legend is not entirely accurate. Scientific research has never
been a strictly individual enterprise (Shapin, 1989), and even Einstein collaborated on several
papers (Pyenson, 1985). In chemistry for example, one third of published papers had more than
one author in 1900, a proportion that grew to 70% by the end of World War II (Gingras, 2010). In
contemporary science, hyperauthorship is rife (Cronin, 2005) and it is rare for a single scientist to
be responsible for a major theoretical breakthrough (Wuchty, Jones, & Uzzi, 2007). In the postWWII era, big science and the large amounts of money required for research have fostered an
environment that encourages research collaboration and the accordant marginalization of the
solitary “genius” (Simonton, 2010; Wuchty, Jones, & Uzzi, 2007). Most research leading to
Nobel Prizes is also the result of collaboration (Zuckerman, 1967), despite the anachronistic fact
that Nobel Prizes cannot be attributed to more than three individuals.
The demise of the single-authored paper in scholarly communication had long been predicted
(Price, 1963), and in the hard sciences, there is evidence that “much of the cutting-edge work
these days tends to emerge from large, well-funded collaborative teams involving many
contributors” due to the increasing specialization witnessed in all research fields (Simonton,
2013, p. 602). In parallel with the rise in the number of authors, we have also observed a growth
in the number of internationally co-authored papers (Larivière, Gingras & Archambault, 2006;
Sonnenwald, 2007), and many studies have shown a correlation between collaboration and impact
at the micro, meso, and macro levels (Franceschet & Costantini, 2010; Narin, Stevens, &
Whitlow, 1991). For example, Wuchty, Jones, and Uzzi (2007) found that while “solo authors did
produce the papers of singular distinction…in the 1950s…the mantle of extraordinarily cited
work has passed to teams by 2000” (p. 1038).
Although a variety of studies have demonstrated a connection between scientific impact and the
various types of collaboration, no study has yet looked at these relationships from a historical
standpoint. The aim of this paper is to perform an analysis of relationship between collaboration
and impact using a dataset of 32.5 million papers and 515 million citations received over the
1900-2011 period. With the aid of this historical dataset, we provide empirical data on the
evolution of the various types of collaboration since 1900 and perform the first historical analysis
of the effect of these various forms of collaboration on citation rates, assessing as well the role of
self-citations. The objective is to understand, quantitatively, whether the relationship between
collaboration and impact has been static across the century. Such stability would suggest a
structural relationship between these two variables, that was unaffected by the rise of citation
indices or the fervor of research assessment exercises in the late 20th century. Furthermore,
analysis of the relationship between impact and collaboration is necessary to make evidencedbased decisions about the allocation of funding and other resources for team science.
Following standard practice, we use co-authorship (that is, the presence of more than one author
on the byline of a scientific publication) as our operationalization of the concept of scientific
collaboration. However, the specific terminology has been disputed. Laudel (2002) argued that
using co-authorship as a proxy for collaboration is based on the faulty assumption that all coauthors are also collaborators and, conversely, that all those who collaborated were listed as coauthors. Katz and Martin (1997) suggested that “[w]hat constitutes a collaboration therefore
varies across institutions, fields, sectors and countries, and very probably changes over time as
well” (p. 16). However, despite these caveats, “co-authorship in publications is widely considered
as a reliable proxy for scientific collaboration” (Franceschet & Costantini, 2010, p. 541) and will
be employed here.
The trend of increasing co-authorship is not a new one nor is the study of the role of collaboration
in science (e.g., Hagstrom, 1965). As early as 1963, Price predicted that scholarly publications
will “move steadily toward an infinity of authors per paper” (p. 89). Recent studies have
confirmed that co-authorship is becoming increasingly common across all disciplines (Cronin,
Shaw, & Barre, 2003; Francheschet & Costanini, 2010; Galison, 2003; Larivière, Gingras, &
Archambault, 2006; Persson, Glänzel, & Danell, 2004; Wuchty, Jones, & Uzzi, 2007). There is
also an upwards trend in the number of authors credited on a paper, which sometimes reaches
triple digits (Abramo, D’Angelo, & Di Costa, 2009).
The collaboration advantage
Several scholars have noted that collaboration is well-suited to the increasingly narrow focus
scientific research (Franceschet & Costantini, 2010; Simonton, 2013), although it has been argued
that increasing specialization cannot fully account for the growth in collaboration (de B. Beaver
& Rosen, 1978). Other scholars have postulated that collaboration is the only practical solution
when one considers the shortage of necessary resources (Wray, 2002), and it has been suggested
that “easier access to public financing; aspirations for greater prestige and visibility resulting
from collaboration with renowned research groups; and opportunities to attain higher
productivity” are other factors that encourage collaboration (Abramo, D’Angelo, & Di Costa,
2009, p. 156). This is, however, not without its complications. For example, it has been suggested
that there may be long-term negative effects when nations engage excessively in collaborations,
rather than constructing their own research capabilities (Wagner & Leydesdorff, 2005).
Price and de B. Beaver (1966) somewhat humorously suggested that the social function of
collaboration is to provide “a method for squeezing papers out of the rather large population of
people who have less than a whole paper in them” (p. 1015). Essentially, collaboration allows for
people with different (and ideally complementary) skills to come together in order to solve a
single problem (Franceschet & Costanini, 2010). This integration, of course, is not always
seamless and can cause friction, wasted time, and possible threats to the quality of the work when
understanding is not reached by all participants (Franceschet & Costantini, 2010). Collaboration
also relies on a healthy balance of trust and bureaucracy (Shrum, Genuth, & Chompalov, 2007)—
the “micropolitics of collaboration” (Atkinson, Batchelor, & Parsons, 1998, p. 260) that must be
negotiated for productive collaboration. Furthermore, collaboration complicates notions of
contribution and responsibility in publication (Birnholtz, 2006; Kennedy, 2003).
Collaboration has been positively correlated with many metrics of academic quality (see
Sugimoto, 2011 for a review). For example, collaboration has been shown to lead to higher
productivity (Abramo, D’Angelo, & Di Costa, 2009; Bordons, Gomez, Fernandez, Zulueta, &
Mendez, 1996; Landry, Traore, & Godin, 1996; Mairesse & Turner, 2005), with productivity
increasing as team size increases (Adams, Black, Clemmons, Paula, & Stephan, 2005). The
citation advantage of multi-authored papers is another incentive for scholars: many studies have
demonstrated that co-authored papers tend to have higher citation impact than single-authored
papers (e.g., Wuchty, Jones & Uzzi, 2007). Similarly, collaborations between industries and
universities (Lebeau, Laframboise, Larivière, & Gingras, 2008) and international collaborations
(Franceschet & Costantini, 2010; Glänzel, 2001; Katz & Hicks, 1997) have also been shown to
yield, on average, higher scientific impact.
The geography of collaboration
Despite the “falling cost and growing ease of communication” among scientists (Katz & Martin,
1997, p. 8), there is evidence of a “‘proximity effect,’ whereby collaboration intensity is inversely
proportional to the distance between the players at stake” (Abramo, D’Angelo, & Di Costa, 2009,
p. 156; see also Cronin, 2008; Gieryn, 2002; Katz & Martin, 1997; Sugimoto & Cronin, 2012;
Yan & Sugimoto, 2011). To incentivize scholars to collaborate across geographic boundaries, a
number of institutional and governmental initiatives have been put into place (Abramo,
D’Angelo, & Di Costa, 2009).
Scholars have the potential to gain academic capital for engaging in collaboration, and a number
of studies have demonstrated a citation advantage for articles co-authored across institutions and
nations (see Ganzi, Sugimoto, & Didegah [2012] for a review of this work). However, this
advantage is not universal. Frame and Carpenter (1979) suggested that international collaboration
is more likely to be witnessed in “basic” fields, and that “extra-scientific factors (for example,
geography, politics, language) play a strong role in determining who collaborates with whom in
the international scientific community” (p. 481). Data on the proportion of papers written in
international collaboration also shows that this proportion is lowest in fields that have more local
values, like social sciences, engineering, clinical research, and highest in disciplines who are
more universal in their objects like mathematics, physics and space science (Gingras, 2002).
Variation is also seen at the country level, where countries with weaker scientific infrastructure
tend to engage more heavily in international collaboration (Luukkonen, 1992). Another (perhaps
more intuitive) finding was that “the larger the national scientific enterprise, the smaller the
proportion of international co-authorship” (Frame and Carpenter 1979, p. 481). There is
compelling evidence that the geographic proximity between the first and last author generate
higher citations (Lee, Brownstein, Mills, & Kohane, 2010) and that international collaborations,
in general, generate higher citations (Glanzel, 2001).
Self-citations have been critically viewed as a gaming mechanism in scholarly communication
(MacRoberts & MacRoberts, 1989), and several studies have examined the prevalence of selfcitations at multiple levels of analysis, including papers, journals, individuals, and countries (Eto,
2003; Frandsen, 2007; Minasny, Hartemink, & McBratney, 2010; Snyder & Bonzi, 1998;
Tagliacozzo, 1977). Early studies found that self-citations ranged from 8% at the individual level
to 20% at the journal level (Garfield & Sher, 1963), while more recent studies have given
percentages as high as 36% (Aksnes, 2003). In addition, some studies have demonstrated that the
rate of self-citation fluctuates between disciplines (e.g., Bonzi & Snyder, 1990). Although
complaints have been leveled at self-citation practices, Glänzel, Debackere, Thijs, and Schubert
(2006) found that, at the macro-level, “there is no reason for condemning self-citations in general
or for removing them from citation statistics” (p. 275).
The citation advantage of co-authored works has been challenged on the grounds that it simply
results from the “amplification” of the known practice of self-citation (van Raan, 1998): that is, if
each author self-cites to the same degree that a single-author would, the citations to a co-authored
paper should be multiplied by the number of co-authors. It should be no surprise that selfcitations increase with the number of co-authors (Wallace, Larivière, & Gingras, 2012), although
it must be noted that this citation rate does not increase linearly (Glanzel & Thijs, 2004),
suggesting that self-citation is not a sufficient explanation for the citation advantage of coauthored works. Instead, a specific citation impact seems to be associated with collaborative work
(van Raan, 1998).
Just as collaboration practices vary by discipline (Larivière, Gingras & Archambault, 2006), so
too does the citation impact of collaboratively written works (Abramo, D’Angelo, & Di Costa,
2009; Pečlin, Južnič, Blagus, Sajko, & Stare, 2012). These studies often lack generalizability due
to small sample sizes, disciplinary focus, and limited time periods for analysis. Additional largescale research is needed to identity the extent to which a citation advantage prevails across time
and discipline. In addition, despite evidence of differences in self-citation by subspecialties, age,
and (to a lesser extent) gender (Hutson, 2006), there is still much research to be done on the
interaction between self-citation and impact.
The data for this paper are drawn from Thomson Scientific’s Science Citation Index Expanded
(SCIE), Social Sciences Citation Index (SSCI), and Arts and Humanities Citation Index (AHCI)
for the 1900-2011 period. We analyze 28,160,453 papers (articles, notes and reviews) and
484,393,178 citations received in Natural and Medical Sciences (NMS) as well as 4,347,229
papers and 30,587,347 citations received in the Social Sciences and Humanities (SSH). The
evolution of the relationship between scientific impact and three types of collaborations is also
presented. These three types of collaboration are: 1) co-authorship (i.e., number of authors), 2)
interinstitutional collaboration (i.e., number of addresses), and 3) international collaboration (i.e.,
number of countries). While co-authorship data are presented here from 1900 onwards,
interinstitutional and international collaboration data are only available from 1973 onwards, as it
was in that year that Thomson Reuters’ predecessor -- the Institute for Scientific Information -began to index institutional addresses in a consistent manner.
Citations are counted from publication year until the end of 2011. In order to have a citation
window of at least two years following the initial publication year, scientific impact data are
presented up until 2009. To take into account different citation practices across subfields of
science and publication year, all citation data were normalized according to the average number
of citations received by the papers that were published in the same year and in the same speciality
(average of relative citations – ARC)1. Accordingly, we have ensured that the “collaboration”
variable is isolated and that the greater impact of collaborative research is not due to disciplines
with higher collaboration rates having greater citation traffic. In order to assess whether selfcitations played a role in the (greater) impact of collaborative research, two types of fieldnormalized citation impact were compiled, one including self-citations and the other excluding
self-citations. In the latter case, all authors’ self-citations – irrespective of their order in authors’
list – were excluded from each paper in the numerator as well as from the denominator itself (i.e.,
the average number of citations of all papers in the respective specialty that were published in the
same year). We did not remove self-citations at the institutional or country level when analyzing
the effect of the evolution of the number of addresses or countries on scientific impact, as it is
individuals who cite, not institutions or countries. We also compiled data (not shown) on the top
5% most cited paper for each of the specialties—the trends were identical to those shown in the
Evolution of collaboration
For all types of collaboration analysed, the numbers of authors, addresses, and countries were
grouped into classes. Figure 1 presents the yearly evolution of the percentage of papers in each of
the classes of number of authors, number of institutional addresses, and number of countries. It
shows that, in all collaboration types, single author/address/country papers are decreasing, both in
NMS and SSH, a finding that has been shown in other studies (Larivière, Gingras &
Archambault, 2006; Wuchty, Jones, & Uzzi, 2007). More specifically, papers with one author
accounted, in 1900, for 87% and 97% of all papers in NMS and SSH respectively; these
percentage are, in 2011, 7% and 38% respectively. At the beginning of the period, the decrease of
the proportion of single-author papers in NMS is due to the increase of papers with two authors;
the proportion of the latter has also decreased since the beginning of the 1960s, mainly due to the
increase of papers with more than two authors. The same phenomenon is observed for papers
with 3 authors at the beginning of the 1980s. In 2011, paper classes with 4-5 and 6-10 authors
account for about 29% and 27% of all NMS papers, respectively. Classes with 11-20 authors
increased their proportion of papers by more than 2000% (0.22% to 4.5%) between 1980 and
2011, while papers with 21 authors or more increased by more than 1000% (0.04% to 0.5%) over
the same period. In the SSH, all paper classes with more than one author increase, although, in
2011, the mode (i.e., the most common number of authors) is still one.
In order to have robust trends in the graphs, only ARC scores based on at least 100 papers are shown.
Figure 1. Percentage of papers by classes of numbers of authors, addresses, and countries, for
natural and medical sciences (NMS) and social sciences and humanities (SSH), 1900-2011
We also observe a decline of the proportion of papers with only one address, from 70% in 1973 to
slightly more than 30% in 2011 in NMS and from 70% to 46% in SSH over the same period of
time. In NMS, we observe a stabilization of the share of papers with two addresses while papers
with three addresses or more are still increasing. Given that SSH journals’ editorial policies
sometimes do not specify the institutional address of authors, approximately 30% of papers from
1975 lacked institutional addressed. This percentage has decreased steadily, although it still
accounts for 8%. In NMS, papers without any address account for only 1% of all papers, down
from 8% in 1973. Some of these papers are actually indexing mistakes, and generally happen in
lower-tier journals.
Papers with authors from two countries also increased their proportion of all published literature,
accounting for 18% of NMS and 14% of SSH literature in 2011. In NMS, papers with three, fourfive, and six or more authors have increased by 2651%, 4969%, and 8365% between 1973 and
2011 while, in SSH, papers with three and four authors or more increased their share of all papers
by more than 3000% and 4300%, respectively. Single country papers are still the mode,
accounting for 77% and 84% of all papers in NMS and SSH, respectively. These data show an
increase of all types of collaboration, both in NMS and SSH. The following sections will assess
how these different types of collaboration and their intensity have influenced papers’ scientific
impact over the course of the last decades.
Inclusion vs. exclusion of self-citations
It is commonly thought that the larger impact of collaborative research is due, at least in part, to
authors’ self-citations (Herbertz, 1995). If a paper contains 20 authors, and each of the authors
cites it at least once, then it accumulates 20 self-citations. At the other end of the spectrum, a
paper with only one author, who cites the paper in a following publication, will result in only one
self-citation. Data presented in Figure 2 show the gain in scientific impact (field-normalized
citation rates) obtained by including self-citations as a function of the number of authors. More
specifically, Figure 2 shows that, in both areas, there is a loss in citation impact when selfcitations are included for non-collaborative research (i.e., one author). In SSH, papers with two
authors obtain similar normalized citation rates whether or not self-citations are included,
whereas papers with at least three authors enjoy a steady increase in impact, gained from
including self-citations. This gain reaches 20% at 25 authors, and oscillates around that
percentage until 40 authors appear on the paper. In NMS, it takes many more authors in order to
benefit from self-citations. Papers with fewer than four authors obtain, on average, lower fieldnormalized scores when self-citations are included than when they are excluded, which is due to
the fact that the self-citations are excluded from both the numerator and the denominator. It is
only when a paper has at least five authors that ARC scores including self-citations rise above
those without self-citations. The gain in impact from self-citations is much smaller in NSE than in
SSH for the same number of authors, which is likely a consequence of the lower number of
citations in these disciplines. These results are consistent with those obtained by Aksnes (2003) in
an analysis of Norwegian papers. In order to remove this self-citation effect—even though it is
small—the data presented in the rest of the paper exclude all authors’ self-citations.
Figure 2. Gain in average of relative citations (ARC) when self-citations are included, as a
function of the number of authors in NMS and SSH, 2005-2009. Three-year moving averages.
The relationship between scientific impact and the number of authors, addresses, and
Figure 3 presents the field-normalized impact of papers for both NMS and SSH, excluding selfcitations, as a function of the number of authors, addresses, and countries. In NMS, the impact
score of papers increases steadily with the number of authors until it reaches about 45 authors,
where it flattens and oscillates, although it remains well above average. The same phenomenon is
also observed in the social sciences. Given the lower proportion of collaborative research papers
in those disciplines, as well as the lower number of papers involved, the impact score tends to
oscillate at the level of 20 authors – although, again, it remains above average. Compared to SSH,
many more authors are required in NMS in order to realize a given percentage of citation gain
from collaboration. SSH start gaining citations with three authors with a roughly linear gain until
20 authors, whereas NMS papers gain citations starting with 5-author papers with no additional
gain in the 10-20 author range. Similar trends are observed when considering the numbers of
addresses and countries: the larger number of addresses and countries appearing on a paper the
larger the impact. Unsurprisingly, papers with no address obtain the lowest impact.
Figure 3. Average of relative citations (ARC) with self-citations excluded, as a function of the
number of authors, addresses, and countries in NMS and SSH, 2005-2009. Three-year moving
averages. Only ARC scores based on 100 papers or more are shown.
Historical evolution of the impact of collaborative research
Figure 4 presents ARC scores for the 1900-2009 period, excluding self-citations, of NMS and
SSH papers for specific classes of author counts. In both areas and for all publication years, we
observe that, on average, papers with fewer authors consistently obtain lower citation rates. It also
shows that there is an inflation of the average number of authors associated with a higher
scientific impact. For example, although papers in the NMS with two or three authors have an
impact larger than the world average in 1900, this has no longer been the case since the first
decade of the 2000s. Since the early 1980s, papers with fewer than 21 authors experience a
decrease in their mean citation rates. A similar trend is also observed for SSH, although a lower
number of authors is needed, on average, to obtain a larger impact. We also see that a larger
number of authors yields a larger comparative impact in the NMS than in SSH.
Figure 4. Average of relative citations (ARC) of papers in Natural and Medical Sciences and
Social Sciences and Humanities, as a function of their numbers of authors, 1900-2009. Three-year
moving averages. Only ARC based on 100 papers or more are shown.
Figures 5 and 6 present the relationship between the number of addresses (Figure 5), countries
(Figure 6), and scientific impact for the 1973-2009 period. It shows that impact increases with the
number of addresses or countries, and that this relationship is consistently observed both over
time and between research areas. We also observe an inflation in the number of addresses
associated with higher scientific impact: over the 1973-2009 period, a decrease in impact is
witnessed for papers with fewer than 11 addresses (in NMS) and papers with fewer than nine
addresses (in SSH). Similar trends are also observed when the numbers of countries is taken into
consideration. On both figures, papers without any address obtain a scientific impact below
average throughout the period.
Figure 5. Average of relative citations (ARC) of papers in the natural and medical sciences and
social sciences and humanities, as a function of their numbers of addresses, 1973-2009. Threeyear moving averages. Only ARC based on 100 papers or more are shown.
Figure 6. Average of relative citations (ARC) of papers in the natural and medical sciences and
social sciences and humanities, as a function of their numbers of countries, 1973-2009. Threeyear moving averages. Only ARC based on 100 papers or more are shown.
Discussion and conclusion
The results presented above show that, from 1900 onwards, co-authorship, inter-institutional
collaboration, and international collaboration have been increasing in both NMS and SSH. More
specifically, single-authored papers decreased in NMS from 87% in 1900 to 7% in 2011 and, in
SSH, from 97% to 38% over the same period. At the beginning of the period in question, the
decrease of single-authored papers in NMS is due to the increase of papers with two authors, the
proportion of the latter has also decreased since the beginning of the 1960s, mainly in favor of
papers with more than two authors. Papers with one address have also been decreasing,
accounting in 2011 for 32% and 46% of all papers in NMS and SSH, respectively. Hence, for
both domains, the majority of contemporary papers are the result of inter-institutional
collaboration. However, despite its increase throughout the period, international collaboration
remains, at the global level, a relatively marginal phenomenon: in 2011, 22.7% and 16.4% of all
papers in NMS and SSH, respectively. Similarly, multilateral collaboration—that is,
collaborations involving more than two countries—only accounted, in 2011, for 5.1% of all
papers in NMS and 2.8% of all papers in SSH. Our findings suggest that while collaboration is
becoming ubiquitous across fields, international collaboration has not seen the same gains as
inter-institutional collaboration. This may be a result of personal mobility (particularly for women
[see Larivière, et al., 2013]) and the national funding policies of large countries such as the U.S.
Our results also provide evidence that the gain in self-citations that papers can obtain increases as
a function of the number of authors, but flattens once a certain number of authors is reached (1012 in NMS and 25 in SSH). In addition, this gain is higher in SSH than in NMS. Finally, the
scientific impact of papers, excluding self-citations, increases with the number of authors,
addresses, and countries appearing on a paper (at least for the 2005-2009 period). This suggests
that self-citation contributes to, but does not fully explain, the relationship between impact and
By providing data on the relationship between co-authorship and scientific impact for the first 50
years of the 20th century, we expand on the work done by Wuchty, Jones, and Uzzi (2007) and
show that, as early as 1900, co-authored papers were more heavily cited than sole-authored
papers. However, with the inflation in the number of contributors over the course of the century,
an increasingly high number of authors is needed in order to obtain a given level of citations. For
instance, while in 1919, papers with three authors had an average impact that was twice the world
average, in 1950, the same impact was obtained by papers that had between 6-10 authors. In
2009, only papers with more than 21 authors reached an average impact that was twice the world
average. For this group of papers, the average impact in 2009 was actually more than three times
the world average. The same “inflation” phenomenon is also observed post-1973, when one looks
at the number of addresses and the number of countries. In other words, when it comes to the
relationship between collaboration and scientific impact, size matters. However, the top tier of
papers with the highest number of addresses and countries did not gain as much in terms of
citations as did the top tier in terms of the numbers of authors.
These results show that, overall, collaborative research results in higher citations rates. This may
also suggest that this relationship is not a “mechanical” artifact caused by an increase in selfcitations, but rather an effect of the greater epistemic value associated with collaborative research
(Wray, 2002). Although there is no single reason that can explain this relationship, one popular
hypothesis is that the most important scientific problems are complex and can only be solved by a
team of researchers having complementary expertise (de B. Beaver, 2004; Wray, 2002). For
example, the pooling of different countries’ human and financial resources in the creation and use
of particle accelerators can actually produce higher scientific impact. Along the same lines, the
equipment needed to carry out such work cannot be handled by a single researcher, let alone by a
single researcher in one area of specialization. One could also mention work in genomics which
involve many institutions and countries. In addition, the complexity of scientific problems often
leads to the forming of interdisciplinary research teams which generate results that are in turn
applicable to each of the areas involved. Finally, the intersubjectivity associated with
collaboration ensures that the resultant knowledge reflects a greater level of consensus and
potentially greater epistemic value than research conducted by an isolated researcher. Future
research should seek to test these hypotheses and further investigate what attributes of
collaborative research contribute to the increased impact of the scientific work it produces.
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